High pressure washing devices, commonly referred to as pressure washers, deliver a fluid, typically water, under high pressure to a surface to be cleaned, stripped or prepared for other treatment. Pressure washers are produced in a variety of designs and can be used to perform numerous functions in industrial, commercial and home applications. Pressure washers typically include an internal combustion engine or electric motor that drives a pump to which a high-pressure spray wand is coupled via a length of hose. Pressure washers may be stationary or portable. Stationary pressure washers are generally used in industrial or commercial applications such as car washes or the like. Portable pressure washers typically include a power/pump unit that can be carried or wheeled from place to place. A source of water, for example, a garden hose, is connected to the pump inlet and the high-pressure hose and spray wand is connected to the pump outlet.
Typically, pressure washers utilize a piston pump having one or more reciprocating pistons for delivering liquid under pressure to the high-pressure spray wand. Such piston pumps often utilize two or more pistons to provide a generally more continuous spray, higher flow rate, and greater efficiency. Multiple piston pumps typically employ articulated pistons (utilizing a journal bearing and wrist pins) or may utilize a swash plate and linear pistons for pumping the liquid. Because these piston arrangements generate a substantial amount of friction (such as for example, sliding friction between the swash plate and pistons), existing pumps are typically oil flooded to provide adequate lubrication. However, such oil-lubricated pumps have several drawbacks. For example, the lubricating oil must be maintained at an adequate level and typically must be periodically replaced. Neglect of such maintenance can result in damage to the pump. Further, the orientation in which the pump may be mounted to the pressure washer frame is severely limited.